The purpose of this study is to compare the long-term clinical efficacy and safety of 1-alpha-acetyl methadol with methadone in the treatment and rehabilitation of heroin addicts. Comparison of the drugs will be done using a group of 28 subjects who are divided into two sub-groups: Subgroup 1 who is receiving methadone and subgroup 2 methadyl acetate. The study is limited to male heroin addicts who volunteered for the initial forty week investigation (IND 10 091) and who have consented to continue for an additional full forty weeks of treatment and who in the Principal Investigator's judgment are suitable candidates for longer treatment. Evaluation of all study patients will include MMPI profiles, EKG, EEG, physical, neurological and psychiatric examinations, weekly urine drug screening, urinalysis, blood chemistry and hematology, vital signs and weight, and symptom-sign record. Both groups will receive the same medical, laboratory, clinical and ancillary services. All stipulations and covenants which have been described in the SAODAP protocol and directions, will be adhered to if this study is awarded to the UCLA applicants.